1. Field of the Invention
This invention relates to a thermal ink-transfer recording material of a thermal melt transfer type.
2. Description of the Related Art
Thermal ink-transfer recording materials having a double-layer structure comprising a support made of polyester or the like and provided thereon a thermal transferring ink layer formed of a binder with a colorant dispersed therein are conventionally put into wide use.
Such thermal ink-transfer recording materials having a double-layer structure, however, have a problem that, when a low-melting wax is used as a binder in order to improve thermal transfer performance, transferred images formed may have a greatly low rub resistance. In order to improve the rub resistance, it has been attempted to use an elastomer resin as the binder. In such an instance, however, there has been a problem that the thermal transferring ink layer adheres to the support in so high a strength that the thermal transferring ink layer may have a low transfer performance and also may make images have a low quality.
Under such circumstances, in order to make the thermal transferring ink layer better releasable from the support and yet make the resultant transferred images have an improved rub resistance, a thermal ink-transfer material is proposed in which a hot-melt layer comprised chiefly of a wax having a penetration of 5 or less is formed between the support and the thermal transferring ink layer (Japanese Patent Publication No. 4-73390). In the thermal transfer recording carried out using this thermal ink-transfer material, the thermal transferring layer is separated from the support, and hence the surface of a transferred image consequently obtained is covered with the hot-melt layer. Thus, the rub resistance of transferred images can be improved.
A thermal printing material is also proposed in which a transparent protective layer comprised of a styrene-methacrylate copolymer and a vinyl chloride resin is formed between the support and the thermal transferring ink layer (Japanese Patent Publication No. 3-18837). In the thermal transfer recording carried out using this thermal printing material, the transparent protective layer comprised chiefly of the resin is separated from the support, and hence the surface of a transferred image consequently obtained is covered with the transparent protective layer. Thus, the rub resistance of transferred images can be greatly improved.
However, in the case when the layer that covers the surface of a transferred image to ensure its rub resistance is a layer comprised chiefly of wax as disclosed in Japanese Patent Publication No. 4-73390, the rub resistance is insufficient for practical use, and it has been sought to more improve the rub resistance.
As for the case when the layer that covers the surface of a transferred image to ensure its rub resistance is a transparent protective layer comprised chiefly of resin as disclosed in Japanese Patent Publication No. 3-18837, the rub resistance can be more improved than the case when the wax is used. In order to realize a good thermal transfer performance, however, the adhesion between the support and the transparent protective layer must be made stronger than the adhesion between the transparent protective layer and the thermal transferring ink layer. For this reason, in the thermal transferring ink layer, it can not avoid using as the binder a resin (a styrene-methacrylate copolymer, a vinyl chloride resin or polymethyl methacrylate) having a high affinity for the resin used in the transparent protective layer. This has brought about a problem that any wax type binders can not be used which are more advantageous than resin type binders in view of materials cost and thermal transfer performance.
As another problem, such a transparent protective layer formed chiefly of resin can not always be separated at the interface between that layer and the support, and is apt to cause cohesive failure in the thermally transferring transparent protective layer or thermal transferring ink layer. In such an instance, the transferred image surface may have a low gloss, resulting in a low image quality. As a still another problem, there are limitations on the material and surface properties of the image-receiving transfer medium side, lacking in general-purpose properties.
The present invention solves the above problems the prior art has had. Accordingly, an object of the present invention is to provide, in an instance where a primer layer capable of covering the surface of a transferred image upon operation of thermal transfer is formed between the support and the thermal transferring ink layer, a thermal ink-transfer recording material that can impart a good rub resistance and a superior surface gloss to transferred images and also can have a good thermal transfer performance even when a wax type binder is used as the binder of the thermal transferring ink layer.
The present inventors have discovered that the above object can be achieved by forming a primer layer constituted chiefly of a resin component and using as the resin component at least two types of resins that are not compatible with each other, thus they have accomplished the present invention.
More specifically, the present invention provides a thermal ink-transfer recording material comprising a support, and a primer layer and a thermal transferring ink layer which are superposed on the support in this order; the thermal transferring ink layer comprising a binder and a colorant dispersed in the binder; wherein;
the primer layer contains at least two types of resins that are not compatible with each other so that the recording material is separable at the interface between the support and the primer layer.